1. Field of the Invention
The present invention relates to an ink-jet recording apparatus which includes a first nozzle group which jets a pigment ink, and a second nozzle group which jets a dye ink.
2. Description of the Related Art
In general, a pigment ink blurs or spreads on a surface of a paper to an extent smaller than a dye ink does. Accordingly, in a conventional ink-jet recording apparatus, when images are recorded with same resolution with the pigment ink and the dye ink respectively, then the pigment ink is jetted such that a volume of a droplet (droplet-volume) of the pigment ink jetted for forming one dot is greater than a droplet-volume of the dye ink jetted for forming one dot. For example, in an ink-jet recording apparatus as described in Japanese Patent Application Laid-open Publication No. 2001-315324, a number of driving waveforms used for jetting the pigment ink is different from a number of driving waveforms used for jetting the dye ink, so that a number of liquid droplets of the pigment ink jetted for forming one dot is greater than a number of liquid droplets of the dye ink for forming one dot.
However, in a method hitherto known in which the volume of the liquid droplet of ink (ink-droplet volume) is changed by changing a number of driving waveforms, there is a limit on the ink-droplet volume which can be controlled. Therefore, there is a problem that it is not possible to meet the demand for further improving recording speed and recording quality. For example, for performing a high-contrast, high-quality recording, there is known an ink-jet recording apparatus in which a pigment ink is used as a black ink, and a dye ink is used as a color ink other than the black ink. Here, when recording a solid-color area (one-color area, area in which recording is performed without a gap or space), with the method for changing the liquid-droplet volume by changing the number of driving waveforms, the number of driving waveforms required for forming one dot with the black ink is greater than the number of driving waveforms for forming one dot with the color ink. For outputting a large number of driving waveforms in a driving cycle, it is necessary to make the driving cycle to be long or prolonged, which in turn makes a recording time to be long. Further, in a high-resolution recording, it is required that the liquid-droplet volume to be further smaller. However, there is a difficulty such that a diameter of a dot, formed with the dye ink used as the color ink, easily spreads on a paper surface to an extent greater than a diameter of a dot formed with the pigment ink used as the black ink, thereby making it hard to achieve a high-quality printing.